Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
GOOD PRACTICE: These guidance notes have been developed by RSD. Whilst every effort has been made to ensure that they are comprehensive, we would refer you to the BCSA publication No 37/04 – BCSA Code of Practice for Metal Decking and Stud Welding – for further guidance. These notes should also be read in conjunction with the prevailing national design guidance and health and safety legislation.
DESIGN
General
RSD decking can be used as permanent shuttering
to an insitu concrete topping, or as both
shuttering and tensile reinforcement to form
what is referred to as a composite floor slab.
Composite floor slabs form the most frequent
application, and these are designed to the
currently applicable design code BS5950: Part 4.
When decking is used as permanent shuttering
only, it is the responsibility of the Project
Structural Design Engineers to specify all the slab
reinforcement necessary to support the
permanent loads, ignoring any contribution from
the decking profile.
RSD provide full working drawings for the steel
deck locations to assist offload and landing of
packs.
RSD will be releasing a unique software package
that enables engineers to design the frame and
decking interaction for composite slabs.
Formwork / Composite Decking
Form decking serves as a permanent formwork
for a reinforced concrete slab, until the slab can
support itself and its live load.
Composite decking serves as a tensile
reinforcement for the concrete slab to which it is
bonded with embossed rib pattern. Composite
action between the concrete slab and the floor
beams or joists can be achieved by welding shear
studs through the decking to the supporting
beam below.
Construction Loading
The design span/load tables generally make
allowance for a temporary construction live load
of 1.5kN/m² in addition to the wet weight of
concrete. This should not be exceeded with
consent of RSD’s Engineer.
The heaping of concrete during placement should
be avoided. In propping condition, it is normally
the construction stage that governs the allowable
spans shown in the tables.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
Construction Loading after Concrete Set
The slab strength will generally have been specified by the Project Structural Design Engineer based on support of long-term loads consistent with the building’s intended use.
In the temporary condition, construction loads from plant used for erecting steelwork or from
materials stored for following trades may constitute a more onerous design condition and
should be referred to the Project Structural Design Engineer for assessment.
Permanent Loadings
The self-weight of the slab has been considered in the design process and need not be included in the imposed loads indicated in the span/load
tables.
The Project Structural Design Engineer should sum all predominantly uniform applied live, partition, finishes and loads when reading from these tables. Any walls other than
lightweight partitions should be considered separately as either line or concentrated loads,
and specific calculations should be made to check the adequacy of the selected slab to
support them.
Reinforcement Mesh
In all circumstances appropriate crack control and distribution reinforcement should be provided within the slab and this can be in the form of a wire-welded mesh or, in certain situations, as macro fibres.
Typically, sheets of mesh reinforcement are 4.8 m by 2.4 m. They must be lapped to achieve continuity of the reinforcement. Lap lengths for mesh reinforcement can be
calculated using methods given in BE EN 1992-1-1, 8.7.5.
The ‘mesh laps’ table shows the calculated lap
lengths for typical wire size and concrete grades, based on the nominal yield strength of 500
N/mm2, and have a cover of at least three diameters.
Decking can only contribute to the transverse
shear reinforcement for the distribution of longitudinal shear forces in composite beams
when it is spanning perpendicular to the beam. In addition, it should either be continuous across
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
the beam, or the beam flange be wide enough to allow effective anchorage of the deck using shear studs welded in a staggered pattern.
Bar Reinforcement
Additional reinforcement may also be required to comply with building or other regulations and it is
the customer’s responsibility to ensure that the necessary design checks and approvals have been
granted.
The axis distance of bar reinforcement defines
the distance from the bottom of the ribs to the centre of the bar, which has a minimum
value of 25mm, and a maximum value of the profile height. Where used, bar reinforcement
is placed at one bar per profile trough.
Deflection
Decking will deflect under the weight of wet concrete as it is placed. The design process takes account of this deflection and limits it in accordance with the relevant code of practice.
The additional weight of concrete due to this deflection is factored into this and all subsequent calculations.
No account is taken for any deflection of the
supporting steel frame. Those responsible for the placement of the concrete should be made aware
of all expected deflections when assessing concrete volumes and finishing techniques.
Temporary Support
Temporary support may sometimes be necessary to sustain the dead weight of wet concrete and
any other construction loads.
General guidance is provided by RSD on project specific installation layout drawings and design calculations. The Project Structural Design
Engineer may also specify temporary propping in situations where tighter control on deflections is deemed necessary.
The design and safe installation of temporary
supports, including any bracing necessary, is the responsibility of the Project Structural Design
Engineer. There should be continuous sole and header plates across the full width of every
propped bay and the system should be installed to ensure zero deflection of the deck at propped
points prior to concrete placement.
Lower Limit for Pre-installation of Temporary Supports. Temporary supports should remain in
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
place until the concrete has reached a minimum of 70% of its characteristic strength.
The header plate should offer a wide area of support so as not to locally compromise the structural integrity or the appearance of the
decking. Except where specifically advised, all temporary props to unsupported slab edges are
to be fully in place prior to installation of the edge trim or decking.
Shear Studs
Shear studs are manufactured from low carbon steel with minimum values of yield point of 350 N/mm2, ultimate tensile strength 450 N/mm2,
and elongation 15%.
The studs should be headed and for through deck welding they should be specified with a shank
diameter of 19mm. Studs should protrude a minimum of 35mm above the shoulder of the
decking profile and the covering of concrete over the head of the stud should be a minimum of
15mm. The shear capacity of headed studs embedded in
solid concrete is calculated in accordance with BS EN 1994-1-1 cl. 6.6. In composite slabs the studs may be affected by the proximity of the webs of the steel decking sheet and their capacity may be reduced. Refer to BS EN 1994-1-1 cl. 6.6 for reduction factor formulae.
DELIVERY
Delivery, Transportation and Access
Loads are normally delivered by articulated vehicles of approximately 16 metres in length and
with maximum gross weights of up to 36 tonnes. Decking will normally be delivered in full loads.
Suitable access to and from unloading points on
sites must be provided and maintained by the client.
Delivery vehicles have a maximum unloading time of 2 hours. Unless otherwise agreed in writing before delivery, offloading and lifting to level and
position is the responsibility of the customer.
Lengths of decking manufactured in accordance with RSD layout drawings or customer schedules are normally consolidated into compact, banded bundles. These bundles may weigh up to 1.5 tonnes and cover an effective area up to 100 square metres when laid, depending on the profile, gauge and length of the panels being delivered.
The maximum sheet length on a project could be
governed by one or more of the following: manual handling limitations, support
configuration, transportation and access for loading deck bundles onto the steel frame.
Identification
Where appropriate, bundles will be marked to
correspond with RSD layout drawings, with a bundle label identifying the product, the site, and
a schedule reference code (see extract below).
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
Lifting and Storage
The customer should arrange for bundles to be lifted using two double wrapped chains, with care taken to avoid excessive pressure across the sheets. Careless use of the slings can cause panels to buckle. Under no circumstances should the
bundles or sheets be removed from delivery vehicles by tipping, barring or similar means.
Bundles should be lifted directly from the delivery
vehicle and placed on the building framework at the correct level and in positions appropriate for
installation. Generally, one bundle of decking will be positioned in each steelwork bay. The sides of
the bundles are identified with paint splashes and these marked sides must all face away from the appropriate set out point. Care must be taken to avoid local overloading of the structure.
INSTALLATION
Installation Service
RSD are fully equipped with experienced and
professional installation teams backed up by our
Construction/Design Departments. Operating
throughout the country, installing decking on all
shapes and sizes of projects.
RSD are also externally-accredited to ISO 14001
management systems for health, safety and the
environment. The sheets will have sharp edges
and corners. COSHH data sheets are available for
all hazards/activities associated with the handling
and fixing of RSD decking.
Health & Safety
Decking is manufactured to ISO 9001 from high
yield steel coated with zinc and may be covered
with soluble protective lubricant which does not
adversely affect performance. The sheets will
have sharp edges and corners. COSHH data
sheets are available for all hazards/activities
associated with the handling and fixing of RSD
decking.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
Fall Arrest
It is recommended that appropriate fall arrest systems are used. Generally, safety netting is advised for steel-framed structures; air bags or similar for other structures. Details of the appropriate fall arrest system, together with a
risk assessment covering the safety system installation method, should be included in the
detailed installation method statement prepared by the decking installer prior to commencement
of work.
Fixing and Securing
Prior to the commencement of installation of the decking the supporting structure must be in a sound and stable condition. Steelwork must be adequately restrained and support for the decking must be provided around columns, splices, openings and other
penetrations. Brickwork, blockwork and concrete supports must be adequately cured.
Steelwork Concrete Other Materials (Inc. Block)
50mm 70mm 70mm
Decking MUST be suitably secured to avoid excessive deflection or dislodgement during construction. The fixings should be placed at 300mm maximum spacing at panel ends and 600mm maximum spacing on intermediate supports.
No pedestrian access to the installed decking
should be permitted until it has been securely fixed to the supporting structure and access is
recommended to be limited to essential construction personnel once installation is
complete.
In the case of a steel support structure, low power powder-actuated fastenings such as Hilti X-ENP-19 L15 can be used with the DX 76 fastening tool to make this connection. In situations where shear studs are subsequently to
be welded through the decking, a lighter gauge nail such as Hilti X-DAK 16 can be used with the
DX 460 or DX 36 cartridge tools at the discretion of the Project Structural Design Engineer.
Alternatives to Hilti nails are available through companies such as Spit, or decking can be secured to steelwork using self-tapping screws. Decking may be secured to brickwork, blockwork and concrete supports provided that the top surface is flat and level and that the top course of
bricks or blocks are of solid construction. Special masonry fixings, such as the Hilti HPS-1
Hammer Screw and Hilti X-SW Soft Washer Fastener can be considered, but in all instances, it
is recommended that the decking installer refers to the fixing manufacturer’s recommendations for the system to be used.
Refer to Hilti data sheet DS 699 Issue No. 02
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
Decking may be cut on site to accommodate notching around obstructions such as columns, but this may affect the design of the sheet and its spanning capability. In such situations special consideration should be given as to the adequacy
and completeness of bearings and to the spanning capability of cut sheets, adjacent sheets
and the finished floor slab.
A petrol-driven disc cutter is the preferred
method for cutting deck sheets and edge trim on site. It is recommended that all profiles are seam-stitched at regular intervals along their length using self-tapping screws. Care should be taken to ensure that the seam stitch screws effectively penetrate and engage with the under-lapping deck sheet.
Decking on Shelf Angles
Where decking is required to be supported on shelf angles, the following checks are made to
ensure it is physically possible to place panels of sufficient length to achieve 50mm minimum end
bearings. Similar arrangements are necessary where the decking panels sit on the bottom
flanges of steelwork.
The shelf angles are structural supports and the Project Structural Design Engineer should ensure that they are fit for purpose. In addition, it is important that the angles project a minimum of 50mm beyond the top flange of the steel beam to
enable a cartridge tool or similar to be used to secure the decking to the supporting structure.
SHEAR STUDS
Shear studs are normally welded through the
decking to the top flange of the steel beam. To avoid burn through of the beam flange the studs
should be welded directly above the web (on the beam centreline) or the flange should have a minimum thickness of 0.4 times the shank diameter (0.4 d = 7.6mm generally). It is preferable to limit the number of studs to a maximum of 2 per trough, wherever possible. As the number of studs increases beyond this limit, the decking becomes more susceptible to localised heat warping and weld splatter can interfere with subsequent welds.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
An alternative to welded shear studs is the Hilti X-HVB shear connector. These connectors are ‘L’ shaped galvanised steel sections that are secured to the steel beam flange using the Hilti DX 76
powder actuated tool. The mechanical properties of the HVB connectors are different to those of
welded studs and a substitution should not be made without the consent of the Project
Structural Design Engineer.
A greater number of X-HVB connectors are needed to provide the same degree of shear
connection as when using welded studs, and particular attention should be paid to the space
available for placing these within the confines of a steel decking profile.
Preparation of Steel Flanges
Any impurities present at the welding interface will lead to a decrease in weld quality. RSD’s profiles are formed from steel with a Z275 galvanised coating and the through deck welding process can be successfully applied to this material provided that the top flange of the steel
beam is not primed, painted or galvanised and is also free from dirt, grease and loose rust. Light rusting that occurs after shot blasting is acceptable. In the welding zone, the decking should fit closely against the beam top flange, a
condition that can generally be assured by the installer at the time of welding.
Stud Installation Equipment
The preferred method for welding shear studs is through the use of mains power. The supply
should be 3 phase with 415 V / 150 A per phase. The welding convertor, measuring 0.5m cubed and weighing 0.5 tonne, is connected to this supply through a watertight 150 amp plug and socket.
Where access for the welding rig to within 7.5m
of the frame is restricted, a steel section may be welded to the frame and extended to a position
from which the 7.5m access rule may be applied. This steel section should, as a minimum, be a steel plate measuring 100 x 10mm.
In situations where access for the mobile rig is restricted and mains power is not available, a
static generator can be provided. This 200 KVA generator is housed in a unit measuring 3m long,
2m wide and 2m high and with a gross weight of 5 tonnes.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
This unit will emit diesel fumes when in operation and should be positioned on the structure in a well-ventilated area which is verified as suitable for this purpose by the Project Structural Design Engineer. Consideration should also be given to
the method of safely re-fuelling the unit and to the safe storage of fuel in a bunded diesel
bowser on the site.
PRIOR TO CONCRETE PLACEMENT
Forming Openings
The following guidelines are offered for forming openings in a slab. It is the responsibility of the Project Structural Design Engineer to ensure the slab will be adequate to support the design imposed loads after the formation of any openings.
RSD’s responsibilities exclude the design, supply or installation of any framing or reinforcement
and the boxing out of decking to form openings. Openings can be classified in terms of the width
measured perpendicular to the span of the decking:
1) Up to 300mm wide – No special treatment is
required. The opening should be boxed out and the decking only cut out using a reciprocating saw
or nibbler when the slab has cured. 2) Between 300mm and 700mm wide – The
opening should be formed as above but additional reinforcement bars should be designed
and added as necessary to spread the load laterally around the opening, supplement the slab
strength immediately parallel to the opening, and control crack widths at corners.
3) Over 700mm wide – Structural trimming steel should be added to the framing arrangement
before the decking is installed.
Health and Safety note: Due consideration should be given to the means of providing protection against falls and accidental passage through of materials at whatever stage openings are formed in the slab. One method that can be used is to
provide a temporary cover to the opening using unconcreted decking secured to a special edge
trim.
The three size categories, outlined here, relate to
isolated openings. If openings are grouped such that a gap of less than 1.5 times the width of the
largest opening exists between them, then consideration should be given to the combined
width.
REFERENCES – HEALTH & SAFETY
British Standards compliant
The following instructions are designed to help composite flooring contractors.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
Composite Floor Deck
1. BS 5950: Part 4 1994. Structural use of steelwork in building: Code of practice for design of composite slabs with profiled steel sheeting.
Composite Steel Beams
2. BS 5950: Part 3: 1990. Design in composite construction: Section 3.1: 1990. Code of practice
for design of simple and continuous composite beams.
Profiled Steel Deck
3. BS 5950: Part 6 1995. Structural use of steelwork in building: Code of practice for design of light gauge profiled steel sheeting.
Fire Resistance
4. BS 5950: Part 8 2003. Structural use of steelwork in building: Code of practice for fire resistant design.
Concrete
5. BS 8110: Part 1: 1997 Structural use of concrete: Code of practice for design and construction. 6. BS 8110: Part 2: 1985 Structural use of
concrete: Code of practice for special circumstances.
Reinforcement
7. BS 4483: 2005 Specification for steel fabric for the reinforcement of concrete. 8. BS 4449: 2005 Specification for carbon steel
bars for the reinforcement of concrete. 9. BS 4482: 2005 Steel wire for the reinforcement of concrete products specification.
Eurocode 3 and 4
10. EC3 ENV 1993 - 1 - 3: 2001 Design of steel structures. Supplementary rules for cold formed thin gauge members and sheeting. 11. EC4 ENV 1994 - 1 - 1: 1994 Design of
Composite steel and concrete structures. General rules for building.
12. EC4 ENV 1994 - 1 - 2: 2001 Design of composite steel and concrete structures.
Structural fire design. 13. SCI - P - 076: Design guide on the vibration of floors. SCI in association with CIRIA (1989).
Health and Safety
Handling Hazards
Handle Zinc coated steel decking with care as it may be delivered with soluble protective layer of oil which can cause contamination to lacerated skin. You should also wear adequate protective gloves and clothing when handling decking as it will have sharp edges and corners.
Eye Hazards
Always wear eye protectors conforming to the specification in BS 2092:1987 when breaking the strapping around bundles as the sudden release
of tension creates can be very hazardous. You should also wear eye protection when cutting
steel as flying particles of metal can also be very dangerous.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
Noise Hazards
Make sure you wear adequate ear defenders when handling or cutting decking and shot firing as the noise levels can be hazardous.
Respiratory Hazards
Fumes containing oxides of iron and zinc are produced during welding or flame cutting and if
inhaled these may cause metal fume fever; this is a short-lasting condition with symptoms similar
to those of influenza. In conditions of exposure to such hazards, the use of respiratory equipment is
recommended.
Explosives and Fumes
Take extra care when using shot fired fixings as explosives and fumes can create hazards.
Occupational Exposure Limits
Limits for iron and zinc oxides are 5g/m> (8 hours TWA) and 10mg/m< (10 minutes TWA). (OE recommendation)
Summary of Protective Measures
Make sure that you wear adequate protective gloves and clothing and safety goggles. Ensure adequate ventilation and use personal protective equipment. Follow the instructions for safe handling, use, disposal and control of cartridges issued by equipment supplier. Ensure adequate ventilation and/or use personal respiratory protective equipment. Use appropriate ear defenders or earplugs.
General Safety Points
Make sure you follow the good practice outlined here and in SCI publications:
• Always fix deck securely before using as a working platform.
• Always employ personal safety measures such as hard hats and protective clothing.
• Always employ all site safety measures such as safety nets, edge protection, and properly tied ladders.
• Don’t leave any unfixed decking sheets.
• Don’t cut holes/voids in the deck before concreting.
• Don’t place props on uncured concrete. • Don’t put heavy loads on unprotected deck.
• Don’t heap concrete or drop from any height.
Guidance Notes for Design and Fixing
Data sheet GN01 - June 2018
JUST A FEW REASONS WHY TO USE
COMPOSITE FLOORING FROM RSD
Sustainability benefits of composite floor construction
Composite flooring systems offer clients and designers several benefits which address the
social, environmental and economic dimensions of sustainable construction.
Speed of construction
Composite flooring systems facilitate fast track
construction; up to 400m2 of decking can be installed by one team in a day! Speed, simplicity of design and affinity for steel-framed buildings make composite floors the system of choice where time, and hence speed of construction, are key drivers. Steel decking can be ordered from us and delivered to order, efficiently stacked on
lorries that can carry many square metres of decking in a single load.
Rapid construction minimises plant hire costs, cranage. The use of the decking as a safe working
platform during construction, speeds up the work of others and follow-on
trades and offers logistical benefits on congested sites. The minimal steel reinforcement required
can be fixed quickly and large areas of floor poured using pumped concrete.
By shortening the construction programme, the
impacts on neighbours and the public within the vicinity of the construction site, such as noise,
dust and traffic congestion are minimised.
Resource efficiency Composite flooring systems are structurally efficient, thereby minimising the resources used in constructing the building (particularly concrete) and reducing the waste generated when it is necessary to deconstruct it. Less concrete means
fewer site deliveries and less localised traffic congestion.
Composite floor systems are stiffer, stronger and lighter than many other floor systems. This means that the weight and size of the primary
structure and the foundations can often be reduced again minimising resource consumption
and end-of-life waste generation.
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